Inverter system

ABSTRACT

An inverter system which converts DC input into AC output and supplies the AC output to a load such as an FL tube detects change in a circuit current due to anomaly such as discharge without contacting with a current route. Relating to an inverter which converts DC input into AC output and supplies the AC output to a load, change in a circuit current of the inverter is detected through the medium of magnetic flux change due to the change in the circuit current caused by discharge. For example, if change in a current occurs in the circuit current of the inverter by disconnection discharge or ground-fault discharge occurring in a current route including a load of the inverter, magnetic flux change occurs in circuit wiring and a space of a core gap of a transformer of the inverter. The change in the circuit current is detected through the medium of the magnetic flux change without contacting with the circuit wiring or the transformer.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Divisional of application Ser. No. 10/620,597entitled INVERTER SYSTEM, filed Jul. 17, 2003, now pending, the entirecontents of which are incorporated by reference herein. This applicationalso claims priority to Japanese Application Nos. 2002-212666 &2003-183034 filed Jul. 22, 2002 and Jun. 26, 2003, respectively, alsoincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an inverter system for feeding ACoutput to various loads such as a fluorescent light tube for use as thebacklight of a liquid crystal display. In particular, the presentinvention relates to a current detection method of an inverter fordetecting change in a circuit current caused by disconnection dischargeof circuit wiring of the inverter, proximity discharge between highvoltage and low voltage parts of the circuit wiring, and so on, throughthe medium of magnetic flux change. Further, the present inventionrelates to a current detection circuit thereof, an anomaly detectionmethod thereof, an anomaly detection circuit thereof, a display device,an electronic device such as a display device and an informationprocessing device, a test method, and a test device.

2. Description of the Related Art

For a liquid crystal display (LCD), a fluorescent light tube (FL tube)is used as a light source for backlight use, and an inverter is used asa lighting device. The inverter adopts a constant current circuit foradjustment of luminance, and so on, and the FL tube is driven by aconstant current to be lit up with a low current of about several mA ata high voltage, for example, in the order of 1.5 kV. A current routeincluding the FL tube to which AC output from the inverter is suppliedcorresponds to a segment of wiring, leading from a winding of aninverter transformer, on the high voltage side thereof, to the FL tube,and is susceptible to deformation under external pressure because it islong and thin in size since it passes by way of a multitude of memberssuch as windings of the inverter transformer, a conductor pattern on aprinted circuit board, connectors, wiring, etc. With a cellular phoneand a note type personal computer, an installation space for the FL tubelighting device is particularly narrow, so that thin wiring leading fromthe inverter to the FL tube is susceptible to deformation due toexternal pressure.

In case that disconnection occurs to the above-described current routeof the inverter, flow of current is cut off by the disconnection,however, there arises a risk of the current route being maintainedbecause the constant current at the high voltage flows in the currentroute of the FL tube, and a rise in voltage occurs at the time of thedisconnection, thereby resulting in continuation of discharge at a spotof the disconnection. When the current route is maintained, currentflows in the tube, so that the FL tube remains lit up. Since it isimpossible to know behavioral anomaly from a lighting state, discoveryof that behavioral anomaly is delayed. Continuation of such an anomalousstate is not preferable.

Therefore, concerning an inverter for feeding AC output to various loadssuch as a fluorescent light tube for use as the backlight of a liquidcrystal display, technical development which relates to a device foravoiding the continuation of anomaly and displaying such anomaly bydetecting anomaly of disconnection discharge of circuit wiring,dielectric breakdown discharge between high voltage and low voltageparts and ground-fault discharge is desired.

Concerning a technology relating to detection of behavioral anomaly ofan inverter and avoidance of continuation of the behavioral anomaly, asearlier patent documents, the Japanese Patent Laid Open Publications No.6-140173, No. 11-121190, No. 9-113546 and so on are in existence.

According to the Publication No. 6-140173, as a protecting device for adischarge lamp lighting system, even if a discharge lamp is lit out atthe time of anomaly, inconvenience to maintain the operation of atransistor inverter is avoided wherein an output of the inverter istaken out to monitor an oscillation condition by a monitor circuit, andanomaly occurring at the oscillation condition due to a short circuitinside the discharge lamp and so forth is detected by a monitoring pulsevoltage so as to stop the operation of the inverter by stopping the feedof a DC voltage, and light out the discharge lamp. However, such aprotection device is complex in configuration because it requires themonitor circuit for taking out the output of the inverter and monitoringthereof, a microcomputer for determining whether the monitoring pulsevoltage is normal or anomalous, and so forth, and also since the outputof the inverter is taken out to an outside, the inverter side is forcedto take measures to cope with the change in an operating condition.

Further, according to the Publication No. 11-121190, as a discharge lamplighting device, noting that a high frequency voltage value is loweredwhen the high frequency voltage to be fed to an discharge lamp isdischarged between a ground and a low voltage part, the high frequencyvoltage is detected by a high frequency voltage detection resistorconnected to the discharge lamp, and the high frequency voltage isrectified to be converted into a DC voltage, and when a level of the DCvoltage is in anomalous level, the discharge lamp lighting device isstopped in operation. However, the discharge lamp lighting devicerequires the high frequency voltage detection resistor directlyconnected to the discharge lamp, and also the difference in voltage atthe time of normal and that at the time of anomaly (at the time ofdischarge) is determined by a voltage dividing ratio of a resistancevoltage divider circuit configured by the high frequency voltagedetection resistor and a threshold level of a switching transistor, andso forth, and hence the accuracy of determination of whether it isnormal or anomalous is low, and also there is a risk of stoppage ofoperation by a level change at the time of normal. Even with thedischarge lamp lighting device, since high frequency voltage detectionresistor is connected to the high voltage part side to detect a highfrequency voltage, special measures for changing a circuit condition andtaking out the detection voltage are required.

Furthermore, the Publication No. 9-113546 relates to an overcurrentdetecting circuit, and discloses that a current transformer detecting acurrent fed to a load from a switching power source section is used. Theovercurrent detecting circuit controls a switching power source sectionby an overcurrent detection signal which is caused based on a detectionof an overcurrent fed to the load, and makes DC output voltage droopfrom the switching power source section to the load. This overcurrentdetecting device is not a device which detects change in a circuitcurrent due to discharge occurring a current route or a load side.

Meanwhile, if there occurs discharge at a spot of the break of circuitwiring and between high voltage and low voltage parts, an electricchange due to that discharge can be checked. When discharge occurs to adisconnection spot, a voltage value or current value representingdischarge is increased inside the inverter, but the amount of change issmall, and hence even if the detection voltage is simply compared with areference voltage, when the difference in level therebetween at the timeof anomaly and normal is small, an erroneous operation is easy to occur,and hence it is not practical. In order to enhance accuracy of thedetection of disconnection discharge or dielectric breakdown dischargebetween high and low voltage parts, a circuit having the combination ofa differentiation circuit, a timer circuit and so forth is required,which however renders the circuit complex, which increases inmanufacturing cost by adding a circuit like this to the inverter,resulting in lack of practice. In the case where the amount of change inwaveforms is small at the time of normal behavior and at the time ofdischarge such as a very small discharge, sufficient accuracy ofdetection cannot be obtained even if a differentiation circuit is used,so that an erroneous operation is easy to occur and it lacks inreliability.

In the case of driving a load such as an FL tube by using a inverter, itis indispensable for maintenance of reliability of operation of aninverter and a load side thereof to discover disconnection discharge ordischarge between high voltage and low voltage parts occurring in thecurrent route and to prevent the continuation of an anomalous state.However, these problems are not disclosed in the Publications No.6-140173, No. 11-121190 and No. 9-113546, and means for solving theproblems is not presented either.

Further, an obstacle due to very small discharge of an LCD is a defectdue to assembly work of the LCD. Although that defect is detected by avisual confirmation and so on, certainty and reliability of thatdetection are lower. Many of ground-fault discharge occurring between ahigh-voltage part and the ground around thereof are due to damageoccurring in a covering of a high-voltage wiring, engagement betweenparts of wiring, a tear of an insulating tube of a soldered part, and soon, and is also due to an impression of stress to semiconductors in theLCD. Because of this, an additional test of dielectric strength isrequired. Further, disconnection discharge of a high-voltage currentroute is due to disconnection of a soldered part, contact fault of aconnector, disconnection of a wiring, and so on. Although an electricdetection method of discharge like this is performed by observation ofcurrent waveform, preparation of a testing equipment and time of a testare longer. Further, for an inspection, a visual confirmation of anappearance is also performed. Even a product to which such a test hasbeen performed, a detection of a fuming obstacle occurring after thelapse of time is difficult. Therefore, in the LCD, a test method and atest device which can discover an obstacle such as disconnectiondischarge and ground-fault discharge with ease and can obtain a testresult with high reliability are desired.

SUMMARY OF THE INVENTION

The present invention relates to an inverter for converting DC inputinto AC output so as to feed the AC output to a load such as an FL tubeand so forth, and it is an object of the invention to detect change in acircuit current caused by discharge with ease, without contacting with acurrent route.

Another object of the present invention relates to an inverter forconverting DC input into AC output so as to feed the AC output to a loadsuch as an FL tube and so forth, and is to previously avoid anunforeseen accident by stopping the continuation of power supply at thetime of anomaly.

Still another object of the present invention is to provide anelectronic device, such as an information processing device, of whichreliability of display is improved.

Still another object of the present invention relates to a test methodand a test device using an inverter for converting DC input into ACoutput so as to feed the AC output to a load, and is to provide the testmethod and the test device which can obtain a test result with highreliability.

In order to attain the above objects, a current detection method of aninverter according to the present invention is a current detectionmethod of an inverter which converts DC input into AC output andsupplies the AC output to a load, and has a construction that detectschange in a circuit current through the medium of magnetic flux changedue to the change in the circuit current of the inverter caused bydischarge.

If disconnection discharge occurring in a current route including a loadof the inverter or proximity discharge namely ground-fault dischargebetween high voltage and low voltage parts of a circuit wiring arise,current change occurs in a circuit current of the inverter, and thatchange makes magnetic flux change occur at a circuit wiring and at aspace of a core gap of a transformer. Therefore, if the change in thecircuit current is detected through the medium of the magnetic fluxchange, the change in the circuit current can be detected withoutcontacting with the circuit wiring and the transformer. By this, it ispossible to know anomaly such as discharge occurring in the currentroute from that change.

In order to attain the above objects, a current detection circuit of aninverter according to the present invention is a current detectioncircuit of an inverter which converts DC input into AC output andsupplies the AC output to a load, and has a construction that provides acurrent detection part (30) for detecting change in a circuit currentthrough the medium of magnetic flux change due to the change in thecircuit current of the inverter caused by discharge. That is, with thecurrent detection part, the magnetic flux change is detected, and thechange in the circuit current due to that magnetic flux change is takenout without contacting with the circuit wiring. Therefore, it ispossible to know anomaly such as disconnection discharge or ground-faultdischarge which occurs in the current route.

In order to attain the above objects, in the current detection circuitof the inverter according to the present invention, the currentdetection part may also be constructed so that a detecting conductor (acurrent detection line 36) is provided adjacent to a space of a core gapof a transformer (an inverter transformer 22) or a circuit wiring (16,etc.) of the inverter, and so that magnetic flux change occurring in thecircuit wiring or the space of the core gap of the transformer isdetected by the detecting conductor. According to a construction likethis, if current change occurs in the circuit current by disconnectiondischarge or ground-fault discharge of a current route, magnetic fluxchange corresponding to the change in the circuit current occurs in thecircuit wiring and the space of the core gap of the transformer. If themagnetic flux change acts on the detecting conductor, high voltage isgenerated. Since this high voltage depends on the change in the circuitcurrent due to the magnetic flux change, the change in the circuitcurrent can be easily detected by the high voltage, and it is possibleto know anomaly such as disconnection discharge or ground-faultdischarge occurring in the current route. In this case, since themagnetic flux change is detected by a simple construction which onlydisposes the detecting conductor in proximity to the circuit wiring, aninfluence of the current detection is not exerted to a circuit of theinverter side, and the change in the circuit current can be detectedwith high accuracy without an erroneous operation, without contactingwith a circuit wiring and so on, and without relating to the operationof the inverter. Further a circuit construction is not complicatedwithout requiring a differentiation circuit and so on, either.

In order to attain the above objects, an anomaly detection method of aninverter according to the present invention is an anomaly detectionmethod of an inverter which converts DC input into AC output andsupplies the AC output to a load, and has constitution that detectschange in a circuit current through the medium of magnetic flux changedue to the change in the circuit current of the inverter caused bydischarge, and detects based on that detection result whether or notanomaly exists in a current rote including the load.

According to constitution like this, based on whether or not a level ofthe change in the circuit current detected through the medium of themagnetic flux change without contacting exceeds a predetermined level,it is possible to know whether or not anomaly exists in the current roteincluding the load, with ease.

In order to attain the above objects, an anomaly detection circuit ofthe inverter according to the present invention is an anomaly detectioncircuit of the inverter (2) which converts DC input into AC output andfeeds the AC output to a load (an FL tube 4), and comprises a currentdetection part (30) and a detection signal output part (a comparator34). The current detection part is a construction that detects thechange in the circuit current through the medium of magnetic flux changedue to the change in the circuit current of the inverter caused bydischarge, and the detection signal output part is a construction that,according to a result of detection of the current detection part,outputs a detection signal representative of whether or not anomalyexists in the current route including the load.

In a construction like this, if anomaly such as disconnection dischargeor ground-fault discharge occurs in the current route between theinverter and the load under a state that high-voltage output is suppliedfrom the inverter (2) to the load such as the FL tube (4), a circuitcurrent of the inverter is changed, and the change in the circuitcurrent causes magnetic flux change (Δφ) to occur to the circuit wirings(14, 16, 52, 54, 70, 72). With the inverter for feeding a high voltageoutput to the load, even if the current route is disconnected, dischargeoccurs in the disconnection spot and the current route is maintained. Inthis case, there occurs the change in circuit current due to thecontinuation of discharge which causes magnetic flux change to occur tothe circuit wiring. Further, when ground-fault discharge occurs betweenthe high voltage and low voltage parts at the output side due todielectric breakdown, the discharge causes the occurrence of an abruptchange in the circuit current, the change in the circuit current causesan abrupt magnetic flux change (Δφ) to occur to the circuit wirings. Byaction of the magnetic flux change, in the current detection part, thechange in the circuit current is detected, and high voltagerepresentative of that change is taken out. By this, in the detectionsignal output part, a detection signal representative of whether or notanomaly such as disconnection discharge or ground-fault discharge in thecurrent route including a load of the FL tube and so on exists isobtained. Therefore, it is possible to indirectly know whether or notanomaly exists in the current route without touching a circuit currentand voltage of the inverter side.

In this case, since the change in the circuit current is detectedthrough the medium of the magnetic flux change, the change in thecircuit current can be detected without contacting, without relating toa circuit construction of the inverter side, and without addingmodification to the circuit conditions of the inverter, and it ispossible to monitor whether or not anomaly exists in the current route.

As described above, according to the anomaly detection method and theanomaly detection circuit, behavioral anomaly such as disconnectiondischarge of the circuit wiring, the dielectric breakdown discharge andso forth can be detected without an erroneous operation with a simpleconstruction without requiring a complex circuit. Since the change inthe circuit current caused by discharge and so on can be detectedthrough the medium of the magnetic flux change which occurring to thecircuit wiring, behavioral anomaly can be detected with high accuracyfrom an anomalous waveform generated due to disconnection discharge ofthe circuit wiring, discharge between the high voltage and low voltageand so forth, and also the detection accuracy is high, and further theoccurrence of behavioral anomaly can be immediately detected. Further,since the change in the circuit current can be indirectly detectedwithout touching the circuit wiring, the current change detection part,detection signal output part, and control part can be configuredindependently of the circuit configuration at the inverter side, withoutinfluencing on or changing the circuit configuration of the inverter orload and without requiring a specific part or circuit such as a complexdifferentiation circuit and so forth.

In order to attain the above objects, in the anomaly detection circuitof the inverter according to the present invention, the inverter mayalso be constructed so that a control part (an inverter control part 20)stops an inverter operation upon reception of the detection signal atthe time of behavioral anomaly. Since the inverter operation is stoppedwhen anomaly such as disconnection discharge or ground-fault dischargeoccurs in the current route, the inverter and the load can be protectedfrom continuation of behavioral anomaly, and it is possible to improvesafety and reliability of the inverter.

In order to attain the above objects, a display device according to thepresent invention has the current detection circuit of the inverter orthe anomaly detection circuit of the inverter, and displays the stop ofa inverter operation or anomaly at the time of the anomaly.

The display by the display device includes image display, sound ofbuzzer, other sound information notice and so forth. The display devicereceives a detection signal from the detection signal output part andperforms the following operations at the time of behavioral anomaly.

-   -   (1) Display of behavioral anomaly such as disconnection        discharge and ground-fault discharge,    -   (2) Display of stop of the inverter operation,    -   (3) Display of either (1) or (2) or both (1) and (2).        It is possible to easily detect behavioral anomaly and the stop        of the inverter operation from these displays so that necessary        measures can be taken as soon as practicable.

According to a construction like this, behavioral anomaly or the stop ofinverter operation is displayed at the time of behavioral anomaly, it ispossible to easily detect behavioral anomaly or stop of the inverteroperation from the display, thereby improving a protection function, andenhancing a reliability of the inverter operation.

In order to attain the above objects, an electronics device such as aninformation processing device according to the present invention is aconstruction that provides the current detection circuit of theinverter, the anomaly detection circuit of the inverter, or the displaydevice. According to an information processing device like this, alighting device for driving an illumination load such as a dischargetube and so forth and a power supply system such as a power supplycircuit and so forth can be constructed using the inverter of thepresent invention. Further, if the information processing device isconstructed using the current detection circuit and/or the anomalydetection circuit of such an inverter, behavioral anomaly such asdisconnection discharge and ground-fault discharge can be discovered, orcontinuation of behavioral anomaly can be avoided, the display ofbehavioral anomaly or the display of the stop of inverter operation canbe displayed, and also confirmation of an operating condition can beperformed with ease, thereby facilitating the protection of the displaydevice of the information processing side. Still further, a reliabilityof a power supply device of various circuits can be enhanced, and theinformation processing device can be protected from continuation ofbehavioral anomaly of a power supply system, thereby contributing to areliability of the operation.

In order to attain the above objects, a test method according to thepresent invention is a test method using an inverter which converts DCinput into AC output and supplies the AC output to a load, and hasconstitution that detects the change in the circuit current through themedium of magnetic flux change due to the change in the circuit currentof the inverter caused by discharge, and decides based on a result ofthat detection whether or not anomaly exists in the current routeincluding the load.

In order to attain the above objects, a test device according to thepresent invention has an inverter which converts DC input into AC outputand supplies the AC output to a load, and a current detection part whichdetects the change in the circuit current through the medium of magneticflux change due to the change in the circuit current of the invertercaused by discharge, and decides based on a result of that detectionwhether or not anomaly exists in the current route including the load.

According to constitution like this, the change in the circuit currentdue to disconnection discharge or ground-fault discharge of a currentroute, and soon, is detected through the medium of magnetic flux change,and anomaly such as disconnection discharge or ground-fault discharge ofthe current route is detected from a result of that detection with easeand with high accuracy. Further, according to this test, it is possibleto decide whether or not anomaly exists without giving an electricalinfluence to a current route of a load side of which power source issupplied from the inverter.

Therefore, according to the test method and the test device, the powersource is supplied to the current route including a load to which the ACoutput of the inverter is supplied and the test is performed. Because ofthis, whether or not anomaly such as disconnection discharge orground-fault discharge occurring in the current route exists is detectedwith ease, and a test result with high reliability can be obtained. Bythis, it is possible to improve reliability of various kinds of productssuch as an FL tube and a liquid crystal display unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and attendant advantages ofthe present invention will be appreciated as the same become betterunderstood by means of the following description and accompanyingdrawings wherein:

FIG. 1 is a circuit diagram of an FL tube lighting device according toan embodiment of a current detection method of an inverter, a currentdetection circuit thereof, an anomaly detection method thereof and ananomaly detection circuit thereof of the invention;

FIG. 2 is a drawing showing an example of a current detection part ofthe FL tube lighting device;

FIG. 3A is a drawing showing a waveform at the time of normal behaviorof the FL tube lighting device;

FIG. 3B is a drawing showing a waveform at the time of behavioralanomaly of the FL tube lighting device;

FIG. 4 is a circuit diagram showing the FL tube lighting device at thetime of anomaly;

FIG. 5A is a circuit diagram showing a case where a primary winding ofan inverter transformer is served as a current detection point, asanother part of the current detection point;

FIG. 5B is a circuit diagram showing a case where a secondary winding ofan inverter transformer is served as a current detection point, asanother part of the current detection point;

FIG. 6A is a perspective view showing a case where a core is used as acurrent detection part;

FIG. 6B is a perspective view showing a case where a current detectionline wound around a core is used as a current detection part;

FIG. 6C is a drawing showing a case where a current detection line woundaround a circuit wiring is used as a current detection part;

FIG. 7 is a drawing showing another embodiment of a current detectionpart;

FIG. 8 is a drawing showing a construction which detects leakage flux ofa core gap of an inverter transformer;

FIG. 9 is a circuit diagram showing an embodiment of a display deviceaccording to the present invention;

FIG. 10 is a flow diagram showing behavioral anomaly verificationprocessing;

FIG. 11A is a perspective view showing a cellular phone using aninverter, as an embodiment of an information processing device accordingto the present invention;

FIG. 11B is a perspective view showing a note type personal computerusing an inverter, as another embodiment of an information processingdevice according to the present invention;

FIG. 12 is a drawing showing an embodiment of a test device according tothe present invention;

FIG. 13 is a flow diagram showing procedure of a test; and

FIG. 14 is a drawing showing the result of an experiment of the currentdetection part according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of a current detection method of an inverter, a currentdetection circuit thereof, an anomaly detection method thereof and ananomaly detection circuit thereof according to the present invention isexplained by referring to FIG. 1. FIG. 1 shows an FL tube lightingdevice according to an embodiment of the present invention. The FL tubelighting device constitutes an FL tube lighting device used as abacklight of a liquid crystal display (LCD).

The FL tube lighting device 1 is provided with an inverter 2 forconverting DC input into AC output, an FL tube 4 serving as a load towhich the AC output is fed, and an anomaly detection circuit 6 connectedto the inverter 2 for detecting disconnection discharge and dielectricbreakdown discharge occurring to a circuit wiring.

The inverter 2 has DC input terminals 8, 10 for receiving DC input andthe DC input terminals 8, 10 are connected to a DC power source 12 fromwhich DC input to be converted into AC output is fed. The DC powersource 12 includes various DC power sources such as a battery, an AC-DCconverter, and so forth. Circuit wirings 14, 16 are connected to the DCinput terminals 8, 10 so as to form a current route of a DC inputcurrent and an input smoothing capacitor 18 is connected to the circuitwirings 14, 16. The circuit wirings 14, 16 are formed of, for example, aconductor pattern on a printed circuit board, and the input smoothingcapacitor 18 constitutes a filter for removing fluctuation component ofa voltage ripple and the like included in the DC input and smoothes outa fluctuating DC input so as to stabilize it. The DC input is fed to aninverter control part 20 through the DC input terminals 8, 10 and thecircuit wirings 14, 16. The inverter control part 20 comprises, forexample, not shown, push-pull inverter circuit part formed of multipletransistors serving as switching elements, a drive circuit part, aswitching controller, and so forth, and it also constitutes anoscillation circuit including a primary winding 24 of an invertertransformer 22 and so on in a feedback circuit. In this embodiment, theinverter control part 20 incorporates a switch 26 for switching supplyof power to the circuit wiring 14. The switch 26 switches over supply ofpower from outside on the basis of a control input fed to a latch inputterminal 28 serving as a control input part of the inverter control part20. A known device such as a general-purpose control IC (TI, TL5001, andso forth) which is already available in a market can be used as theinverter control part 20, and hence a detailed circuit configuration isomitted.

In the inverter 2, the anomaly detection circuit 6 for detectingbehavioral anomaly comprises a current detection part 30 for detecting acircuit current, a current change detection part 32 for detecting acircuit current change caused by discharge, and a comparator 34 servingas anomaly determining means for determining whether a change level ofthe detected circuit current is anomalous or not.

The current detection part 30 is a circuit part which detects a changein the circuit current through the medium of a magnetic flux changecased by the change in the circuit current from the circuit wiring 16 ofthe inverter 2, and so on. In this embodiment, the circuit wiring 16side of the inverter 2, which is a lower potential side thereof, is setas a current detection point. In the current detection part 30, acurrent detection line 36 is provided as a detecting conductor whichdetects the change in the circuit current through the medium of amagnetic flux change Δφ that occurs to the circuit wiring 16. In thiscase, DC input current id is a detection target in connection with thechange in circuit current, to be detected. The current detection line 36is arranged in the vicinity of the circuit wiring 16, and at such aspacing therefrom as allowing the magnetic flux change Δφ occurringthereto to be detected.

Next, the current detection part 30 is explained by referring to FIG. 2.FIG. 2 shows an example of the current detection part 30. The currentdetection part 30 is constituted by the current detection line 36 havingthe same wiring pattern as the circuit wiring 16 provided on a printedcircuit board 38, and, in this embodiment, the wiring patterns of thecircuit wiring 16 and the current detection line 36 constitutes parallelpatterns. That is, the current detection line 36 having a straight-linesegment parallel with the circuit wiring 16 in a straight-line form isdisposed, and the magnetic flux change Δφ occurring to the circuitwiring 16 due to a change in the DC input current id is caused to act onthe current detection line 36. In this case, a reference letter “a” iswidth of the current detection line 36, a reference letter “b” is lengthof the current detection line 36, and a predetermined insulating spacingD is set between the current detection line 36 and the circuit wiring16. Sensitivity in detection of the magnetic flux change Δφ is enhancedby rendering the insulating spacing D narrower.

The current detection line 36 is provided with detection terminals 40,42, for taking out a voltage, generated through the agency of themagnetic flux change Δφ, and a detection voltage obtained across thedetection terminals 40, 42 is fed to a current change detection part 32for detecting change in circuit current. In case of this embodiment, thecurrent change detection part 32 is provided with a diode 44 serving asa conversion part for rectifying the detection voltage to be convertedinto a DC level, and the diode 44 is connected to the detection terminal40 side of the current detection part 30 while a capacitor 46 as afilter circuit together with a resistor 48 constituting a adjustmentpart of a detection level are connected between the cathode side of thediode 44 and the detection terminal 42. For the diode 44, use is madeof, for example, a Schottky diode having short reverse recovery time inorder to cope with detection of current change due to disconnectiondischarge and so forth. The current change detection part 32 of such aconfiguration as described is constituted as a current-voltageconversion part for converting a change in the circuit current into achange in a DC voltage, so that the DC voltage corresponding to thechange in the circuit current is obtained at the capacitor 46 and theresistor 48, and a voltage level thereof represents the change in thecircuit current, which is a change in the DC input current id in thiscase.

A detection signal from the current change detection part 32 is fed to acomparator 34 constituting a detection signal output part. Thecomparator 34 is, as well as an amplification part for amplifying thedetection signal, a decision part for determining on the basis of achange level of the detected circuit current whether or not thebehavioral anomaly exists, comparing the detection signal with apredetermined level displaying the behavioral anomaly. In this case, thepredetermined level represents a reference level with which it ispossible to determine that there exists behavioral anomaly such as, forexample, disconnection discharge of the circuit wiring, proximitydischarge (dielectric breakdown discharge) between high voltage and lowvoltage parts of the circuit wiring, and so forth, and the predeterminedlevel may be set at any level such as a level at the time of normalbehavior, a level slightly higher than the level at the time of normalbehavior, and so forth, provided that determination on whether thebehavior of the inverter is anomalous or normal can be made.Accordingly, the comparator 34 compares the detection signal with thepredetermined level, outputting a detection signal Vs that turns to alow (L) level displaying normal when, for example, a detection voltagelevel is not higher than the predetermined level, and a detection signalVs that turns to a high (H) level displaying anomaly when the detectionvoltage level exceeds the predetermined level. The detection signal Vsis fed to the latch input terminal 28 of the inverter control part 20,and is used for maintaining operation of the inverter control part 20 atthe time of normal while stopping the operation of the inverter controlpart 20 at the time of anomaly. With the present embodiment, the switch26 is caused to open at the time of anomaly by the detection signal Vsfed to the latch input terminal 28. Thereby, supply of power to theinverter control part 20 is cut off, and operation of the inverter 2 iscontrolled so as to be in the off condition.

Further, circuit wirings 52, 54 are connected to a secondary winding 50of an inverter transformer 22, thereby constituting a current route ofoutput current. A ballast capacitor 56 is interposed within one of thecircuit wirings 52, and is connected to a connector 58 as an AC outputterminal while a constant current detection resistor 60 is interposedwithin the other of the circuit wirings 54, and is connected to aconnector 62 as an AC output terminal. An FL tube 4, which is a load, isconnected to the respective connectors 58, 62, constituting a backlightof an LCD 64. The ballast capacitor 56 constitutes a stabilization partfor stabilizing tube current flowing in the FL tube 4, and the tubecurrent detected by the constant current detection resistor 60 is fed tothe inverter control part 20 side to be used for keeping the tubecurrent constant. Accordingly, as a switching action of the invertercontrol part 20, AC is generated by a DC to AC conversion actionthereof, and at the same time, high frequency output at high voltage isprovided to the secondary winding 50 of the inverter transformer 22 dueto step-up in voltage of the inverter transformer 22. This high voltageoutput is fed to the FL tube 4 via the circuit wirings 52, 54, and theconnectors 58, 62, respectively. The present embodiment shows a casewhere the single FL tube 4 is connected to the single secondary winding50. However, a plurality of FL tubes may also be installed, and, in thatcase, the ballast capacitor 56 is installed for every FL tube.

Next, operation of the FL tube lighting device is explained by referringto FIG. 3 and FIG. 4. FIG. 3A shows an operating waveform at the time ofa normal condition, FIG. 3B shows an operating waveform at the time ofan anomalous condition, and FIG. 4 shows a case that disconnectiondischarge or ground-fault discharge is occurring in a current route.

Upon driving the FL tube 4 with a constant current by use of theinverter 2 as described above, the FL tube 4 is lit up with a constantdriving current. In the case of normal behavior, a behavior waveform ofAC output will be a sinusoidal waveform nw as shown in FIG. 3A, however,if a break occurs to, for example, the circuit wiring 54 as shown inFIG. 4, discharge occurs to a spot 66 of the break, thereby maintaininga current route. A behavior waveform at the time of such an anomalousbehavior as above will be an anomalous waveform composed of thesinusoidal waveform nw occurring at the time of the normal behavior witha discharge waveform dw superimposed thereon as shown in FIG. 3B. Thedischarge waveform dw represents a noise (high frequency) undergoing anabrupt change from a fundamental waveform of the gently-sloping ACoutput and having a high frequency component, however, such a waveformcomponent does not cause an increase in amperage of the circuit current,but only causes an increase in change increment of the circuit current.Further, the discharge waveform dw occurs periodically in relation to achange in level of the sinusoidal waveform nw occurring at the time ofthe normal behavior. Such a phenomenon as described occurs to not onlycurrent waveform but also voltage waveform, however, it has beenconfirmed on the basis of experiments that change occurring to currentwaveform is greater than that for voltage waveform.

If a current route is maintained due to the discharge described, thereoccurs a rapid change to circuit current including output current i₂ ofthe inverter transformer 22, input current i₁ of the invertertransformer 22, the DC input current id, drive current inside theinverter control part 20, and so forth, so that an intense magnetic fluxchange Δφ, displaying an abrupt change in circuit current, occurs aroundthe circuit wirings 14, 16, constituting the current route. Hereupon, anabrupt magnetic flux change Δφ is detected by the current detection line36, and a high voltage displaying a change in the circuit current isgenerated across both ends of the current detection line 36. Since thehigh voltage is rectified by the diode 44 and smoothed out by thecapacitor 46, a DC voltage at a level displaying an abrupt change incurrent can be obtained at the time of discharge. The DC voltage is fedto the comparator 34, and is compared with the predetermined level,whereupon the comparator 34 obtains the detection signal Vs thatdisplays whether the behavior is normal or anomalous.

When the detection signal Vs is fed to the latch input terminal 28 ofthe inverter control part 20 as an output of the stop of the operation,the switch 26 of the inverter control part 20 is turned into the offcondition, thereby stopping inverter operation and canceling AC output,whereupon the FL tube 4 is turned into unlit condition, and at the sametime, continuation of discharge is interrupted. As a result, theinverter 2 and the FL tube 4 are released from continuation ofbehavioral anomaly.

In case that a discharge 68, displayed by a broken line in FIG. 4,occurs due to dielectric breakdown and so forth, caused by proximitybetween a high voltage part on the AC output side and a low voltage parton a chassis, and so forth, a behavior waveform at that time will becomean anomalous waveform composed of the sinusoidal waveform nw occurringat the time of the normal behavior with the discharge waveform dwsuperimposed thereon as shown in FIG. 3B as with the case ofdisconnection discharge.

In this case as well, an abrupt change in circuit current of the circuitwiring 16 causes a magnetic flux change Δφ to occur. The magnetic fluxchange Δφ is detected by the current detection line 36 of the currentdetection part 30, and consequently, the comparator 34 obtains adetection signal Vs displaying behavioral anomaly. As a result, theinverter operation by the inverter control part 20 is stopped and ACoutput is cancelled, whereupon the FL tube 4 is turned into unlitcondition, and at the same time, continuation of discharge isinterrupted. Similarly, the inverter 2 and the FL tube 4 are releasedfrom continuation of behavioral anomaly.

With the present embodiment, since the current detection part 30 isinstalled on the input current side of the inverter control part 20, itis possible to detect through the medium of the magnetic flux change Δφa rapid change in the input current, occurring due to behavioral anomalycaused by disconnection discharge, dielectric breakdown discharge, etc.in the current route on the output side, thereby causing a high voltagerepresenting behavioral anomaly to occur across the detection terminals40, 42. That is, the present embodiment is easier to cope withinsulation as compared with the case of detecting behavioral anomaly onthe high voltage side, and is also excellent in safety.

Further, with a very simple configuration wherein the current detectionline 36 is disposed in parallel with the circuit wiring 16, it ispossible to generate a voltage displaying a rapid change in the circuitcurrent because a change in the circuit current is detected through themedium of the magnetic flux change Δφ, and in addition, to take out thechange in the circuit current at high voltage. That is, sensitivity indetection of the change in circuit current is high and behavioralanomaly can be detected with high accuracy.

Further, although it is possible to detect behavioral anomaly in such asdischarge and so forth from the change in voltage, the change in thecircuit current is detected through the medium of the magnetic fluxchange Δφ, so that the accuracy of detection is enhanced. That is, thechange in waveform caused by discharge is larger in the change incurrent waveform rather than the change in voltage waveform, and themagnetic flux change Δφ occurs due to this change in current, and hencethe accuracy of detection of behavioral anomaly through the medium ofthe magnetic flux change Δφ is enhanced.

When detecting the change in the circuit current through the medium ofthe magnetic flux change Δφ, the magnetic flux change Δφ can be detectedwith ease by a very simple configuration having the current detectionline 36 which is arranged in parallel with the circuit wiring 16, andfurther the current detection line 36 can be installed without addingany change in the circuit condition at the inverter 2 side, and also itis possible to configure the circuit arrangement of the current changedetection part 32 and the comparator 34 irrespective of the inverterside circuit in response to a high voltage generated at the detectionterminals 40, 42, and hence the circuit configuration can be designedwith ease.

Further, the current change detection part 32 can obtain a DC voltagehaving a level necessary for determining whether a high voltage obtainedat the detection terminals 40, 42 is normal behavior, or behavioralanomaly caused by discharge with a simple circuit configuration andprocessing such as rectification by the diode 44, the smoothing out bythe capacitor 46, and so forth. That is, it is possible to generate a DCvoltage in which normal behavior or behavioral anomaly caused bydischarge clearly appears in the difference of level thereof.Accordingly, the comparator 34 can easily set a reference level forsharply differentiating between normal behavior and behavioral anomaly,and hence the accuracy of detection is high and behavioral anomaly canbe detected without an erroneous operation.

When the detection signal Vs obtained by the comparator 34 is fed to thelatch input terminal 28 of the inverter control part 20, the operationof the inverter control part 20 is stopped at the time of behavioralanomaly, and thereby the load such as the inverter 2, the FL tube 4 andthe LCD 64 can be protected from continuation of behavioral anomaly.

Meanwhile, it is confirmed, according to an experiment, for theoccurrence of detection voltage at the current detection line 36 whichis irrespective of disconnection discharge or dielectric breakdowndischarge, that the current detection line 36 can detect the variationin voltage caused by the change in circuit current due to very smalldischarge by setting a circuit condition therein such that use is madeof, for example, a Schottky diode having short reverse recovery timeserving for the diode 44 of the current change detection part 32, andthe resistor 48 has a resistance value in the order of, for example, 0.1MΩ to 5 MΩ, the capacitor 46 has an electrostatic capacitance in theorder of 0.0015 μF to 0.1 μF, and so forth. As a result, it is possibleto detect an anomalous condition such as disconnection discharge,dielectric breakdown discharge or ground-fault discharge, and alsopossible to prevent easily an erroneous operation caused by excessivecurrent when power is turned on, and so forth. In this case, althoughconcrete circuit conditions of the diode 44, the capacitor 46, theresistor 48 used in the experiment are exemplified, they can bearbitrarily set, and the invention is not limited to such circuitconditions.

Next, a current detection point at which change in a circuit current isdetected is explained by referring to FIG. 5. FIG. 5A shows a case thatthe current detection point is set to a primary side of the invertertransformer, and FIG. 5B shows a case that the current detection pointis set to a secondary side of the inverter transformer.

The current detection point, as shown in FIG. 5A as an example otherthan the circuit wiring 16 shown in FIG. 1, may be set to circuitwirings 70, 72 respectively connected to a primary winding 24 of theinverter transformer 22, the current detection part 30 is installed inthe circuit wiring 72, and a current detection line 36 may be arrangedin the vicinity of the circuit wiring 72. Further, as shown in FIG. 5B,circuit wirings 52, 54 connected to a secondary wiring 50 of theinverter transformer 22 may be set as a current detection point, and,for example, a current detection part 30 is installed in the circuitwiring 54 and a current detection line 36 may be arranged in thevicinity of the circuit wiring 54. When the current detection line 36 isarranged in the vicinity of the circuit wiring 72, behavioral anomalycan be detected through the medium of the magnetic flux change Δφ due tothe change in a primary current namely an input current i₁ which flowsin the circuit wirings 70, 72 at the side of the primary winding 24 ofthe inverter transformer 22, thereby stopping the inverter operation.

Further, if the current detection line 36 is arranged in the vicinity ofthe circuit wiring 54, the change in an output current i₂ can bedetected through the medium of the magnetic flux change Δφ caused by thechange in the output current i₂ which is the secondary current of theinverter transformer 22 flowing through the circuit wiring 54, and theinverter operation can be stopped at the time of behavioral anomaly, andhence an inverter 2, an FL tube 4 and so forth can be protected fromcontinuation of behavioral anomaly such as discharge and so forth. Inthis case, the change in a waveform is larger at the output side of theinverter transformer 22 compared with that at the input side thereof,and also the change value of the discharge waveform is remarkablyincreased. Because of this, a circuit current change and a magnetic fluxchange are larger, and the accuracy of detection is enhanced.

Next, other embodiments of current detection part 30 are explained byreferring to FIG. 6. FIG. 6A shows a current detection part 30 which isconstituted by using a core, FIG. 6B shows a current detection part 30which is constituted by winding a current detection line around a core,and FIG. 6C shows a current detection part 30 which is constituted bywinding the current detection line 36 around the circuit wiring 16, 54or 72.

In connection with an embodiment of a current detection part 30, asshown in FIG. 6A as an example, a ring-shaped core 74 is installed inthe current detection part 30. Circuit wirings 16, 54 or 72 and acurrent detection line 36 are allowed to pass in the core 74, and acommon magnetic path which passes magnetic flux φ may also be formed inthe current detection line 36 together with the circuit wirings 16, 54or 72 with the core 74. When using the core 74, the change in magneticflux change Δφ can be intensified by magnetic permeability μ of amagnetic material forming the core 74, and also a detection voltage ofthe detection terminals 40, 42 can be increased, thereby enhancingsensitivity in detection.

Further, for example, a current detection line 36 may be wound around acore 74 as shown in FIG. 6B. In this case, magnetic flux change Δφacting on the current detection line 36 is intensified by the number ofturns N, and detection voltage generated in detection terminals 40, 42is stepped up, thereby taking out higher detection voltage. In thiscase, circuit wirings 16, 54 or 72 may be wound around the core 74.Further, a cylindrical core may be used as the core 74, and even withthe cylindrical core, a common magnetic path can be formed in thecircuit wirings 16, 54 or 72 and a current detection line 36.

Still further, for example, a current detection line 36 is wound aroundthe circuit wirings 16, 54 or 72 by several numbers of winding, as shownin FIG. 6C, so that the magnetic flux change Δφ occurring to the circuitwirings 16, 54 or 72 may act on the current detection line 36. With sucha configuration, detection voltage corresponding to the number of turnsof the current detection line 36 can be taken out between the detectionterminals 40, 42. With a configuration having no such a core 74, thenumber of parts is decreased, and hence the current detection part 30can be manufactured at low price. According to the anomaly detectioncircuit 6 of the inverter 2 having no the core 74, as shown in FIGS. 1,4 and 5, the same effect as made here can be obtained.

Next, another embodiment of the current detection part 30 is explainedby referring to FIG. 7 and FIG. 8. FIG. 7 shows a current detection part30 which is provided adjacent to an inverter transformer, and FIG. 8shows the detection of a magnetic flux change caused by a dischargecurrent.

An inverter transformer 22 used in the inverter 2 has a gap 25 which isformed in a core 23, and is provided so that the gap 25 is positioned inthe side of a printed circuit board 38. Therefore, a current detectionline 36 is provided on the printed circuit board 38 at a space of thegap 25 by means of a wiring pattern. In other words, the currentdetection line 36 which has width “a” narrower than a space “w” of thecore 23 and length “b” is formed on the printed circuit board 38, thecore 23 of the inverter transformer 22 is provided astride of theprinted circuit board 38, and the current detection line 36 is arrangedin the space of the gap 25. Although the length “b” of the currentdetection line 36 is set larger than width “d” of the core 23, it mayalso be set to the same length (b=d) . Further, to the invertertransformer 22, a primary winding 24 and a secondary winding 50 areprovided. Terminals 24 a and 24 b of the primary winding 24 areconnected to the inverter control part 20, one terminal 50 a of thesecondary winding 50 is connected to the ballast capacitor 56 (FIG. 1) ,and the other terminal 50 b is connected to the constant currentdetection resistor 60.

In a construction like this, for example, if electric discharge occursin a current route of the secondary winding 50 side of the invertertransformer 22, as shown in FIG. 8, a severe magnetic flux change Δφoccurs in the gap 25 by its discharge current. This magnetic flux changeΔφ acts on the gap 25 and the current detection line 36 adjacent to thegap 25 and is detected by the current detection line 36, and a detectedvoltage which is on a high level representative of change in a circuitcurrent (i_(d)) is taken out. This detected voltage is given to thecurrent change detection part 32, and is used for the inverter controland so on.

Next, an embodiment of a display device according to the presentinvention is explained by referring to FIG. 9. FIG. 9 shows a displaydevice using the anomaly detection circuit of the inverter according tothe present invention.

In the display device, the configurations, operations and effects of theinverter 2 and the anomaly detection circuit 6 are the same as thosedescribed with reference to FIGS. 1 to 8.

With the display device in FIG. 9, an LCD 64 and an indicator 76 whichconstitute a display part displaying an anomaly at the time of anomalousbehavior are installed, and a processor 78 is installed as a displaycontrol part of these LCD 64 and indicator 76. The processor 78constitutes a processing part for executing a control program fordisplaying behavioral anomaly stored in a storage part, not shown,wherein a detection signal Vs obtained by a comparator 34 is fed to theprocessor 78 and a keyboard 80 is connected to the processor 78 throughwhich instruction input for executing behavioral anomaly verificationprocessing is inputted. An display driving part 82 is installed in theLCD 64 for executing predetermined display upon reception of a displaycontrol output from the processor 78 and an display driving part 84 isinstalled in the indicator 76.

Operation of this display device is explained by referring to FIG. 10.FIG. 10 is a flow diagram showing behavioral anomaly verificationprocessing. In the verification processing of behavioral anomaly, by astart of that processing, it is determined whether or not the inverteris in behavioral anomaly verification mode (a step S1). In this case,when a specific key of the keyboard 80 or an instruction assigned tomultiple keys thereof are operated, the behavioral anomaly verificationmode is set. In this case, a behavioral anomaly verification mode isautomatically set when power is turned on, anomaly of the inverter 2 maybe confirmed. When the behavioral anomaly verification mode isestablished, the detection signal Vs from the comparator 34 is received,and whether or not behavioral anomaly is detected is decided (a stepS2).

At the time of the normal condition, it is displayed on the LCD 64 orthe indicator 76 that behavioral anomaly does not exist, namely, anormal behavior is performed (a step S3). When a predetermined timeelapses from the start of the display of the normal behavior or anadministrator instructs an operation display cancel from the keyboard80, the display operation is cancelled (a step S4) , and, after that,the processing is returned to the step S1.

When behavioral anomaly is detected in the step S2, the behavioralanomaly is displayed on the LCD 64 or the indicator 76 and the stop ofoperation of the inverter 2 is displayed on the same (a step S5). Theadministrator verifies these displays, and executes necessaryprocessing. For example, when a predetermined time elapses from thestart of the display of behavioral anomaly or the administratorinstructs an operation display cancel from the keyboard 80, the displaycancel is effected (a step S6) , and, after that, the processing isreturned to the step S1. In this case, when behavioral anomaly isdisplayed, the display cancel may not be effected unless theadministrator effects an improvement processing.

When the FL tube 4 namely a light source of the LCD 64 is lit out, it isexpected that content of the display of the LCD 64 is hardly verified.Therefore, although the verification or confirmation of anomaly or astop of the inverter 2 becomes easy by the indicator 76 when displayingbehavioral anomaly or the inverter 2 stops its operation, it is possibleto use the LCD 64 for displaying the behavioral anomaly or the stop ofthe operation of the inverter 2. When the FL tube 4 is in unlitcondition, and the display of such a condition can be verified, theindicator 76 is not always needed. If the display is effected using boththe LCD 64 and the indicator 76, a reliability of the stop of operationand the display thereof can be enhanced.

Next, embodiments of an information processing device, an electronicdevice and so on according to the present invention are explained byreferring to FIG. 11. FIG. 11A shows a cellular phone according to theembodiment, and FIG. 11B shows a note type personal computer accordingto the embodiment. These cellular phone and note type personal computerconstitute the information processing device, the electronic device andso on which are configured to use the anomaly detection circuit of theinverter or display device according to the invention.

With the information processing device, the electronic device and so onshown in FIGS. 11A and 11B, an FL tube 4 is installed, as a backlight ofan LCD 64 serving as a display device, in a housing 90 of a cellularphone 86 or a note type personal computer 88. Further, along with theinverter 2 shown in FIG. 1 or 4 and the anomaly detection circuit 6 ofthe inverter 2 according to the invention as a driving device of the FLtube 4, a processor 78 as an arithmetic and control part, a keyboard 80and so forth are incorporated therein. In this case, an indicator 76serving as an display element is installed inside the housing 90 of thecellular phone 86 or the note type personal computer 88 for use inmaintenance thereof, and it can be installed on an outer face of thehousing 90.

With such a configuration, in the information processing device, theelectronic device and so on of the cellular phone 86, the note typepersonal computer 88 and so forth, behavioral anomaly such as adisconnection discharge, dielectric breakdown discharge of the circuitwirings 14, 16, circuit wirings 52, 54, circuit wirings 70, 72 of theinverter 2 respectively, and so forth can be monitored, and when theoperation of the information processing device is stopped, theinformation processing device, the electronic device and so on can beprotected from continuation of behavioral anomaly. Further, since thebehavioral anomaly or the stop of the operation is displayed on the LCD64 or the indicator 76, the behavioral anomaly or the stop of operationcan be quickly detected from the display thereof, thereby realizing ahigh reliable information processing device, the electronic device andso on. Further, anomaly such as disconnection discharge, dielectricbreakdown discharge of the circuit wirings 14, 16 and so forth of theinverter 2 can be easily determined from the content of the display, andhence necessary measures can be executed quickly, thereby providing theinformation processing device, the electronic device and so on havinghigh safety.

Next, an embodiment of a test meted and a test device according to thepresent invention are explained by referring to FIG. 12 and FIG. 13.FIG. 12 is a drawing showing the test device according to theembodiment, and FIG. 13 is a flow diagram showing procedure of a test.

A liquid crystal display unit 92 is used as a test object. In this case,the liquid crystal display unit 92 has an LCD 64 and an FL tube 4,connectors 58 and 62 are provided to the FL tube 4, and a connector 94is provided to the LCD 64.

A test device 96 of this liquid crystal display unit 92 has the inverter2 providing the anomaly detection circuit 6 described before in FIG. 1,and also provides the processor 78 and the display driving parts 82 and84 described before in FIG. 9. An output of the display driving part 84is given to a display 98, and a test result is displayed on the display98. Other construction is the same as the construction shown in FIG. 1and FIG. 9.

On the occasion of the test of the liquid crystal display unit 92, analternating current output part of the inverter 2 of the test device 96is connected to the connectors 58 and 62, and an output part of thedisplay driving part 82 is connected to the connector 94.

Referring to the flow diagram shown in FIG. 13, if the test is started,whether or not the FL tube 4 is connected to the test device 96 isdecided (a step S11) , and the supply of a power source to the FL tube 4from the inverter 2 is started if the FL tube 4 is connected (a stepS12). As a result of the supply of the power source, whether or notchange in a circuit current is more than a predetermined level isdecided (a step S13). If disconnection discharge or ground-faultdischarge does not occur in a current route of the side of the FL tube 4which is a load, the change in the circuit current due to its dischargecurrent does not occur, and the change in the circuit current becomesunder the predetermined level. The detection of this change in thecircuit current is as described before. In this case, a detected outputof the anomaly detection circuit 6 is given to the processor 78 from acomparator 34, the processor 78 decides that the unit 92 is a normalcondition, and a result of that decision representative of the normalcondition is displayed as a test result on the display 98 (a step S14).On the other hand, if the disconnection discharge or the ground-faultdischarge occurs in the current route of the side of the FL tube 4 whichis a load, great change in the circuit current occurs by its dischargecurrent, and that change becomes above the predetermined level. Thedetection of this change in the circuit current is as descried before.In this case, the detected output of the anomaly detection circuit 6 isgiven to the inverter control part 20, and an inverter output isstopped. At the same time, the detected output is given to the processor78 from the comparator 34, the processor 78 decides that the unit 92 isan anomalous condition, and a result of that decision representative ofthe anomalous condition is displayed as a test result on the display 98(a step S15). Then, after stopping the supply of the power source (astep S16), the liquid crystal display unit 92 which has finished thetest is taken off from the test device 96, a next liquid crystal displayunit 92 is connected to the test device 96, and the same test isperformed.

According to the above-mentioned test device and test method, in respectto the liquid crystal display unit 92, the test can be performed withoutincreasing the number of processes of the test and without doing specialpreparations. Further, it is possible to perform the test under a statethat the condition of lighting of the liquid crystal display unit 92 isset to the same condition as the time of actual use. Therefore, it ispossible to quickly and high-accurately test whether or not thedisconnection discharge or the ground-fault discharge is in existenceand even whether or not anomaly of the connectors 58, 62 and 94 is inexistence. Furthermore, the test can be performed on a manufacturingline. Hence, it is possible to contribute to realization of a producthaving high reliability.

In the above-mentioned test device, the current detection part 30 isprovided at the circuit wiring 16 of the input side of the invertercontrol part 20. However, the present invention is not intended to limitto this construction. The current detection part 30 may also be providedat the circuit wiring 52 or 54 of the secondary side of the invertertransformer 22, the change in a circuit current is detected through themedium of magnetic flux change Δφ due to the change in the circuitcurrent, and anomaly of the FL tube 4, discharge of the current routeand so on may also be decided. As described before, detecting the changein a circuit current of the secondary side of the inverter transformer22 is advantageous for improvement of accuracy of detection.

Further, the present invention includes other embodiments and variouskinds of electronic devices, in addition to the current detection methodof an inverter, the current detection circuit thereof, the anomalydetection method thereof, the anomaly detection circuit thereof, thedisplay device, the information processing device, the test method andthe test device which have been described before.

(a) Although the comparator 34 for comparing a detection voltage with apredetermined level to output a detection signal is exemplified as thedetection signal output part for outputting the detection signalrepresenting behavioral anomaly when the change in a circuit currentexceeds the predetermined level according to the embodiment of theinvention, a switching transistor or a switching circuit which isrendered in a conductive or cut off state upon reception of the level ofthe detection signal may serve as the detection signal output part.

(b) It may be configured that after a detection voltage obtained at thedetection terminals 40, 42 was rectified or a specific frequencycomponent is taken out, it is converted into a digital signal, then thedigital signal is fed to the processor 78 shown in FIG. 9, while theprocessor 78 is configured to serve as a detection signal output part,whereby it is determined whether or not behavioral anomaly occurs in theinverter 2, and output of the determination is fed to the latch inputterminal 28 of the inverter control part 20 as a control input, so thatthe operation of the inverter 2 may be stopped. In this case, behavioralanomaly such as discharge, and so forth and the condition thereof may bedisplayed on the LCD 64 or indicator 76 when stopping the operation.

(c) Although the circuit wiring 16 and current detection line 36 shownin FIG. 2 are formed by a conductor pattern on a printed circuit board,they may be formed of wire rods other than the conductor pattern. Whenthe wire rods are used, the circuit wiring 16 and the current detectionline 36 are bundled to cause the magnetic flux change Δφ at the side ofthe circuit wiring 16 to act on the current detection line 36.

(d) The current change detection of the current change detection part 32may be effected by a detector circuit for detecting and taking outcomponents specific to discharge contained in the change in circuitcurrent occurring due to disconnection discharge or dielectric breakdowndischarge in other than a manner where the detection voltage of thedetection terminals 40, 42 are rectified, smoothed out and taken out bythe diode 44, capacitor 46 and resistor 48.

(e) If the inverter control part 20 dose not have an operation stoppingpart, as a control part which cancels the operation of the inverter 2, aswitching circuit which cancels the supply of power relative to theinverter control part 20 by the detection voltage Vs at the time ofbehavioral anomaly may also be provided at the DC input side of theinverter control part 20.

(f) Although the inverter control part 20 is exemplified as the controlpart, the supply of power to the inverter control part 20 is controlledusing the processor 78 as the control part and the inverter operationmaybe stopped at the time of behavioral anomaly.

(g) Although exemplified is the inverter 2 as a prior art which isdriven by a constant current or outputs a lower current in problem to besolved by the invention, the present invention is not limited to such aninverter.

(h) According to the embodiment of the invention, the primary winding 24of the inverter transformer 22 is formed of a single winding forfacilitating the explanation of the invention, a winding for taking outa feedback signal to be fed to each transistor of the push-pull invertercircuit incorporated in the inverter control part 20 is not excluded,and various inverters are included in the anomaly detection circuit ofthe inverter of the present invention.

(i) The anomaly detection circuit of the inverter has the current changedetection part, and the current change detection part can comprise arectifying part for rectifying a fluctuation voltage obtained by amagnetic flux change, and a smoothing part for smoothing a rectifiedvoltage obtained by the rectifying part. According to a constructionlike this, it is possible to obtain a detection signal having a levelwhich is in proportional to the circuit current change with highaccuracy from a voltage generated in the current detection line, so thatdetection of the circuit current change caused by the very smalldischarge can be effected, thereby enhancing the accuracy of detection.

(j) In the anomaly detection circuit of the inverter, the current changedetection part has a rectifying part for rectifying the fluctuationvoltage obtained by the magnetic flux change, and the rectifying partcan be formed of a Schottky diode. Since the Schottky diode has shortreverse recovery time compared with a high speed diode, the circuitcurrent change due to discharge and a noise component due to dischargeare rectified to take out as a DC component so that the change incircuit current due to very small discharge can be detected, therebyenhancing the accuracy of detection to prevent an erroneous operation.

(k) In the anomaly detection circuit of the inverter, the current changedetection part can be constructed to have the filter for extractingchange in current due to disconnection discharge, dielectric breakdowndischarge, and so forth. According to a construction like this, thechange in circuit current due to discharge except a transient currentchange, for example, when power is tuned on, can be detected withaccuracy, and an erroneous operation can be prevented.

(l) In the current detection circuit of the inverter, the currentdetection part can be constructed to have discrete elements comprising apart of the circuit wirings 14, 16, 52, 54, 70, 72 and the currentdetection line 36 which are independent from one another. According to aconstruction like this, the current change detection part is installedin the circuit wiring of the inverter 2, for example, in the circuitwirings 14, 16, 52, 54, 70, 72 at an arbitrary spot thereof, so that theinverter, and so forth can be protected from continuation of behavioralanomaly such as discharge and so forth, thereby enhancing reliability.

(m) In the current detection circuit of the inverter, the currentdetection part can be installed in an arbitrary spot of the circuitwiring leading from the DC input to the load on, the DC input side inthe circuit wiring, a part on a primary winding and a part on asecondary winding of the inverter transformer 22 provided in theinverter, or on any of the combination of the parts on the DC inputside, the primary and the secondary windings. According to aconstruction like this, behavioral anomaly such as discharge, and soforth can be detected in the circuit wirings 14, 16, 52, 54, 70, 72 atan arbitrary spot thereof.

(n) In the anomaly detection circuit of the inverter, the anomalydetection circuit can be constructed so that the display driving part isincorporated in the control part, and the output thereof is fed to theindicator, thereby displaying behavioral anomaly. According to aconstruction like this, the anomalous state can be easily grasped bydisplaying behavioral anomaly of the inverter and the stop of theinverter operation.

(o) In the anomaly detection circuit of the inverter, the invertercontrol part 20, the current change detection part 32 and the comparator34 can be constructed by a single IC. According to a construction likethis, a reliability of the anomaly detection circuit of the inverter canbe enhanced by the IC, which is single in number and also commercialvalue of a control IC serving as a constituent of the inverter can beimproved, and the number of part can be reduced at the same time.

(p) In the anomaly detection circuit of the inverter, the core 74 forforming a magnetic path which is common to the circuit wirings 14, 16,52, 54, 70, 72 and the current detection line 36 may also be provided.That is, if a magnetic path which is common, for example, to the circuitwirings 16, 54, 72 and the current detection line 36 is formed using thecore 74, the magnetic flux change Δφ at the side of the circuit wirings16, 54, 72 can act efficiently on the current detection line 36 throughthe core 74. In this case, since the magnetic flux is intensified bymagnetic permeability of the core 74 to act on the current detectionline 36, the accuracy of detection of the circuit current change can beenhanced, thereby further enhancing a protecting function of theinverter 2 or the load at the time of behavioral anomaly. The magneticflux change can be intensified by the magnetic permeability of amagnetic material of the core 74 which is a common magnetic path, andhence sensitivity in detection of the change in current can be enhanced.

(q) In the information processing device, the inverter can be used forthe power supply device or the FL tube lighting device. According to aconstruction like this, a high reliable information processing devicecan be provided.

(r) A lighting device provided with the anomaly detection circuit of theinverter can be constructed. According to this construction, thedetection of disconnection discharge and the dielectric breakdowndischarge of the inverter, the stop of the operation, and the displayaccompanied thereby can be effected, thereby providing high reliablelighting device.

Furthermore, the result of an experiment of the current detection part30 is explained by referring to FIG. 14. In the case that, concerningthe wiring pattern of the current detection line 36 (FIG. 2) namely thedetection conductor, the length “b” of the current detection line 36 ismade to change, and also the space “D” between the circuit wiring 16 andthe current detection line 36 is set to D=0.1 mm, 0.2 mm, 0.3 mm and 0.5mm, respectively, under the state that the width “a” of the currentdetection line 36 is set to a=10 mm, voltage shown in FIG. 14 is givento the current change detection part 32. As is clear from the result ofthe experiment, if the space “D” between the current detection line 36and the circuit wiring 16 is set to D=0.5 mm under use of the currentdetection line 36 with the width a=10 mm and the length b=10 mm, it isconfirmed that the detected voltage of 2V is obtained by a dischargecurrent. According to this detected voltage, it is confirmed that thechange in a circuit current due to discharge can be detected with highaccuracy.

Although the best mode for carrying out the invention, the object, theconfiguration and the operation and effect have been described in detailabove, the invention is not limited to such embodiment for carrying outthe invention, and it is a matter of course that the invention can bevariously changed or modified by a person skilled in the art on thebasis of a gist and split of the invention as disclosed in claims andthe detailed description of the invention, and such a change ormodification, and various conjectured configurations, modified examplesand so forth are included in the scope of the invention, and thedescription of the specification and drawings are not restrictivelyunderstood.

The entire disclosure of Japanese Patent Applications No. 2002-212666and No. 2003-183034 including specifications, claims, drawings andsummaries are incorporated herein by reference in their entirety.

1. A current detection circuit of an inverter that converts DC input into AC output and supplies the AC output to a load, comprising: a current detection part, provided at the DC input side of said inverter, that detects magnetic flux change, which occurs in a portion of circuit wiring passing through the current detection part of said inverter based on a change in a circuit current due to discharge occurring in the overall circuit wiring of said inverter, at the DC input side of said inverter, said current detection part detecting the change in the circuit current through the medium of the magnetic flux change; and a current change detection part that inputs a detected output of the current detection part and detects current change, the current change detection part including a rectification part that rectifies a fluctuation voltage obtained by the magnetic flux change and a smoothing part that smoothes a rectified voltage given from said rectification part.
 2. The current detection circuit of claim 1, further comprising: a detecting conductor that is provided adjacent to said portion of circuit wiring, wherein the detecting conductor detects the magnetic flux change occurring in said portion of the circuit wiring.
 3. The current detection part of claim 2, wherein said current detection part constitutes said detecting conductor and a portion of said circuit wiring as an independent discrete element.
 4. The current detection circuit of claim 2 further comprising a core that forms a common magnetic path for said circuit wiring and said detecting conductor.
 5. The current detection circuit of claim 1, wherein said rectification part is constituted by Schottky diode.
 6. The current detection circuit of claim 1, wherein said current change detection part includes a filter that extracts change in a current due to discharge including disconnection discharge and dielectric breakdown discharge.
 7. A current detection circuit of an inverter that converts DC input into AC output and supplies the AC output to a load, comprising: a current detection part that detects magnetic flux change occurring based on a change in a circuit current of said inverter due to discharge that occurs in circuit wiring of the inverter, said current detection part detecting the change in the circuit current through the medium of the detected magnetic flux change; and a current change detection part that inputs a detected output of the current detection part and detects current change, the current change detection part including a rectification part that rectifies a fluctuation voltage obtained by the magnetic flux change and a smoothing part that smoothes a rectified voltage given from said rectification part, wherein a core of a transformer of said inverter has a gap formed in a magnetic path, and said current detection part includes a detecting conductor provided at a space of the gap of the core of said transformer, and detects the magnetic flux change occurring at the space of the gap of the core of said transformer by said detecting conductor.
 8. A current detection circuit of an inverter that converts DC input into AC output and supplies the AC output to a load, comprising: a current detection part, provided at a primary side and/or a secondary side of a transformer of said inverter, detecting magnetic flux change, which occurs in a portion of circuit wiring passing through the current detection part of said inverter based on a change in a circuit current due to discharge occurring in the overall circuit wiring of said inverter, said current detection part detecting the change in the circuit current through the medium of the magnetic flux change; and a current change detection part that inputs a detected output of the current detection part and detects current change, the current change detection part including a rectification part that rectifies a fluctuation voltage obtained by the magnetic flux change and a smoothing part that smoothes a rectified voltage given from said rectification part, wherein said current detection part includes a detecting conductor that is arranged in the vicinity of said circuit wiring and is print-formed on a circuit board with said circuit wiring, and detects the magnetic flux change by said detecting conductor.
 9. A test method using an inverter that converts DC input into AC output and supplies the AC output to a load, comprising: a step that, by a current detection part, detects magnetic flux change, which occurs in a portion of circuit wiring at the DC input side of said inverter based on a change in a circuit current due to discharge occurring in the overall circuit wiring of said inverter, and detects the change in the circuit current through the medium of the magnetic flux change; a step that inputs a detected output of the current detection part to a current change detection part and outputs the detected output of the current detection part as a result of a detection, the current change detection part including a rectification part that rectifies a fluctuation voltage obtained by the magnetic flux change and a smoothing part that smoothes a rectified voltage given from said rectification part; and a step that decides based on the result of the detection of the change in said circuit current whether or not anomaly exists in a current route including said load.
 10. A current detection circuit comprising: a current detection part, provided at a DC input side of an inverter, that detects magnetic flux change occurring in a portion of circuit wiring at the DC input side of said inverter based on a change in a circuit current due to discharge occurring in the overall circuit wiring of said inverter; and a current change detection part that inputs a detected output of the current detection part and detects current change, the current change detection part including a rectification part that rectifies a fluctuation voltage obtained by the magnetic flux change and a smoothing part that smoothes a rectified voltage given from said rectification part. 